This invention relates to a drag reducer and more particularly to a drag reducer for use on the rear of a vehicle such as a tractor trailer truck.
The aerodynamic drag of the back end of a vehicle such as a tractor trailer truck, known as the xe2x80x9cbase drag,xe2x80x9d can comprise more than 20% of the vehicle""s overall aerodynamic drag. Reducing the aerodynamic drag of a vehicle results in improved fuel efficiency and operational cost savings. While much attention has been given to reducing the front end drag of tractor trailers, this has only served to increase the proportion of the overall drag attributable to base drag.
In order to address base drag, a drag reducer must be large and streamlined enough to cause a significant portion of the airstreams along the top and sides of the trailer to remain in laminar flow at the back end of the vehicle without breaking down into turbulent flow and, therefore, causing increased drag. In addition, it is important that any drag reducer added to the back end of the trailer must allow easy access to the cargo area, so it must be easily stowed and moved out of the way of the cargo doors. Further, the drag reducer cannot be so long as to interfere with traffic. There is a plethora of art directed to drag reducers including U.S. Pat. Nos. 2,737,411; 3,425,740; 4,006,932; 4,030,779; 4,142,755; 4,236,745; 4,257,641; 4,451,074; 4,458,936; 4,600,508; 4,682,808; 4,688,841; 4,741,569; 4,702,509; 4,818,015; 4,978,162; 5,058,945; 5,236,347; 5,498,059; 5,823,610; and 6,092,861. This art, however, fails to teach or suggest a drag reducer structure which meets the requirements delineated above. Accordingly, prior art drag reducers have not achieved any market success.
It is therefore an object of this invention to provide a drag reducer for tractor trailer trucks and other vehicles.
It is a further object of this invention to provide such a drag reducer which is easily deployable and stowable.
It is a further object of this invention to provide such a drag reducer which allows easy access to the rear of the trailer or other vehicle.
It is a further object of this invention to provide such a drag reducer including a frame that is hinged to the rear of the vehicle and operable between a position adjacent the rear of the vehicle and a position swung away from the rear of the vehicle to provide access to the rear of the vehicle.
It is a further object of this invention to provide such a drag reducer including an inflatable bag attached to the frame and operable between a deployed inflated configuration when the frame is positioned adjacent the rear of the vehicle and a deflated stowed configuration both when the frame is adjacent the rear of the vehicle and also when the frame is swung away from the rear of the vehicle.
It is a further object of this invention to provide such a drag reducer wherein the inflatable bag includes at least first and second converging panels defining an aerodynamic drag reducing structure in the deployed inflated configuration and the first panel is foldable over the second panel in the deflated stowed configuration.
The invention results from the realization that an improved drag reducer can be achieved by attaching a drag reducing tail to the rear of the trailer such that the drag reducer has sufficient rigidity when deployed to maintain a stable shape that causes a laminar flow of the air converging behind the vehicle and by engineering the tail to be easily stowable and quickly moved away from the cargo doors to allow access to the cargo area.
This invention features a drag reducer including a frame hinged to the rear of a vehicle and operable between a position adjacent the rear of the vehicle and a position swung away from the rear of the vehicle to provide access to the rear of the vehicle. An inflatable bag is attached to the frame and operable between a deployed inflated configuration when the frame is adjacent the rear of the vehicle and a stowed deflated configuration when the frame is adjacent the rear of the vehicle and when the frame is swung away from the rear of the vehicle. The inflatable bag includes at least first and second converging panels that define an aerodynamic drag reducing structure in the deployed inflated configuration. The first panel is foldable over the second panel in the deflated stowed configuration to control the bag in the stowed deflated configuration and to assist configuring the bag in the stowed deflated configuration.
In a preferred embodiment, the inflatable bag is unitary in construction. The inflatable bag may also include an inflatable bladder surrounded by a covering. The first panel may include battens framing the first panel. The battens may be flexible along their longitudinal axis and inflexible off axis.
The frame may have four sides and the bag may have a top panel, a bottom panel and two side panels, one side panel extending from the hinge side of the frame and being foldable over the other side panel, the top panel and the bottom panel. The panels converge at a distal portion of the bag. The bag may also include a base panel spanning the frame to form a proximal portion of the bag adjacent the vehicle.
The frame may be hinged to the side of the rear of the vehicle. There may be a plurality of hinges and the hinges may be double hinges.
The drag reducer may include a fill port for inflating the bag and means for automatically inflating the bag.
The first panel may be biased into a folded position. There may be at least one spring member connected to the first panel to bias it in the folded position. Indeed, all of the panels may be biased into a folded position. Thus, there may be a spring member connected to the top panel to bias it downward, a spring member connected to the bottom panel to bias it upward and a spring member connected to each of the first and second panels to bias them inward.
There may also be a skirt connected to the frame to provide stress relief for the inflatable bag. Typically, the first panel has a length equal to or less than the extent of the frame.
There is also provided a drag reducer including a four sided frame having one side hingeable to the rear side of a vehicle and operable between a position adjacent the rear of the vehicle and a position swung away from the rear of the vehicle to provide access to the rear of the vehicle. The drag reducer includes an inflatable bag attached to the frame and operable between a deployed inflated configuration when the frame is adjacent the rear of the vehicle and a stowed deflated configuration when the frame is adjacent the rear of the vehicle and when the frame is swung away from the rear of the vehicle. The inflatable bag includes panels which extend outward from the frame and converge at a distal portion defining an aerodynamic drag reducing structure. One panel is a dominant panel and is biased to fold over the other panels so that when the bag is deflated it is automatically self-stowing.
In a preferred embodiment, there may be a top panel, a bottom panel and two side panels, one of which is the dominant panel. The dominant panel may extend from the hinged side of the frame. There may be at least one spring member connected to the dominant panel to bias it in the folded position. There may also be spring members connected to the top, bottom and non-dominant side panels to bias them into the folded position under the dominant panel.
The dominant panel may have a length equal to or less than the extent of the frame. The dominant panel may be framed by batten members, and the batten members may be flexible along their longitudinal axis and inflexible off axis.